Hi all, got a problem with both plugs in cylinders 1 & 4 - black with carbon deposits, but maybe I should start from the beginning.
2 weeks ago, the engine waring light came on, then starting flashing. Loss of, and intermittent power, so took it to my local indie. Diagnostics came up with ignition problem on 1 & 4. Both coil packs replaced, but problem still persisted, although light went out and symptoms were not as pronounced. HT leads swapped with a donor vehicle - still no good. Finally new plugs, but still not right. When accelerating it seems fine, but at idle, or just cruising at relatively low revs (2 - 2.5K), it just seems a little 'lumpy'. Sort of misses a little, but not so much you'd actually call it a missfire; just not running smoothly.
So today I thought I'd investigate the state of the new plugs, and found that both plugs on 1 & 4 were really coked up - entirely black with sooty deposits, whereas the other plugs seemed fine.
Any ideas what this could mean?
I've recently had a new MAF (about 500 miles ago), and a new ECU.
All suggestions gratefully recieved.
I should probably add, that cleaning the plugs did not improve the running.